Menopause, reproductive life, hormone replacement therapy and bone phenotype at age 60-64: a British birth cohort.

Abstract

CONTEXT: Previous studies of menopausal age and length of reproductive life on bone are limited by retrospective reproductive histories, being cross sectional, or lacking gold standard bone technologies, or information on hormone replacement therapy (HRT) or surgical treatment. OBJECTIVE: To investigate age at menopause, length of reproductive life and HRT use in relation to volumetric and areal bone mineral density (vBMD, aBMD), bone size and strength in women aged 60-64. DESIGN: A birth cohort study followed for 64 years with prospective measures of age at menarche and menopause and monthly HRT histories. SETTING: England, Scotland, Wales Participants: 848 women with known type of menopause and bone measures at 60-64 years Main outcome measures: Peripheral quantitative computed tomography (pQCT) measurements of the distal radius total and trabecular vBMD; diaphyseal radius total and medullary cross sectional area, cortical vBMD and polar strength strain index (SSI); dual energy x-ray absorptiometry (DXA) measurments of aBMD at the lumbar spine and total hip. RESULTS: A ten year increase in age at natural (but not surgical) menopause was associated with 8.2% (95% CI: 1.3,15.1%, p=.02) greater trabecular vBMD and a 6.0% (95% CI 0.51,11.5%, p=.03) greater total vBMD; findings were similar for length of reproductive life. A ten year difference in HRT use was associated with a 6.0% (95% CI 2.6%,9.3%, p<.001) greater polar SSI and a 0.9% (95% CI 0.4%, 1.5%, p=.001) greater cortical vBMD. These estimates changed little on adjustment. Estimates for aBMD were consistent with those for pQCT. CONCLUSIONS: The positive effects on trabecular vBMD of later natural menopause and longer reproductive life persisted into early old age. HRT use was associated with greater radius cortical vBMD and polar SSI, and spine aBMD.